AbstractObjectiveTo determine an abdominal pressure cutoff value for intra‐abdominal hypertension (IAH) in the horse and characterize IAH in horses with acute colic.DesignProspective clinical cohort.SettingUniversity teaching hospital.AnimalsNine healthy adult horses and 56 horses with acute colic.InterventionsVentral intra‐abdominal pressure (IAP) was measured in triplicate at end expiration and averaged. Each colic case was classified as medical or surgical and large intestine (LI) or small intestine (SI). Management and final outcome (alive, euthanized, or died) were recorded. IAH was defined as ≥32 mm Hg (mean + 2 SDs of ventral IAP in control horses). Proportions of horses with and without IAH for different lesions were expressed as fractions and percentages.Differences in IAP between groups were determined using ANOVA with post‐testing or t‐tests. Odds ratio for management strategy (ie, need for medical or surgical) in horses with IAH was performed using Fisher's exact test. P < 0.05 was considered significant.Measurements and Main ResultsIAP was higher in horses with colic compared to controls (P = 0.025). Over 18 months, 30.4% of horses with colic had IAH (n = 10 LI lesions, n = 7 SI lesions). Horses with LI medical lesions had the highest IAP of all lesions (mean 36.5 mm Hg). IAH horses with medical lesions were 15 times more likely to survive than IAH horses requiring surgery (P = 0.03).ConclusionsAcute colic in horses is associated with an increased ventral IAP compared with healthy controls. IAH does exist in horses with colic, notably LI medical lesions, and is associated with nonsurvival in horses that require surgery.